BRPI0916996A2 - coaxial conduit assembly comprising a thermally insulating sleeve - Google Patents

Abstract

"coaxial conduit assembly comprising a thermally insulating sleeve". The present invention relates to a set of two piping coaxial conduits comprising at least two unitary elements (5a, 5b) of coaxial conduits each comprising an inner conduit (5a2, 5b2) and a conduit ( 5a1, 5b1) with an annular gap (5a3, 5b3), preferably filled with an insulating material, mounted end to end by welding, comprising a hollow tubular wall sleeve (1) of rigid or semi-rigid material preferably plastic or composite material, said conduit wrapping in front of the weld joint (7) of said two coaxial conduit unit members (5a, 5b), said hollow tubular wall of the sleeve having a housing. (1a) and an inner shell (1b) tightly connected at their longitudinal ends (1c), thereby defining an inner volume filled with a virtually incompressible thermal insulating material.

Description

Descriptive Report of the Invention Patent for “SET OF COAXIAL CONDUITS UNDERSTANDING A THERMAL INSULATION SLEEVE”.

The present invention relates to a set of coaxial ducts comprising a thermally insulating sleeve, more particularly. an insulating sleeve for the connection zone of two sections of coaxial ducts. namely, submarine pipelines that carry hot or cold fluids, preferably submarine pipelines aimed at large profound nodes.

In most industrial domains, efficient insulation systems are used to keep the fluids conveyed in the pipelines at a constant temperature, for whatever reason. transfers between equipment can be made at considerable distances, reaching, for example, several hundred meters or even several kilometers. These distances are common across industries. ia * s such as oil refineries, liquefied natural gas facilities (-155 ^:> C), underwater oil fields that extend for several tens of kilometers. These oil fields are developed at ever greater water depths that can exceed 3000 m.

The present invention relates. in particular, to elements of coaxial pipelines intended for the manufacture of subsea pipelines installed in oil fields at great depths, namely, the bottom-surface connection pipes suspended between the seabed and a surface vessel anchored in the said oil field.

These ooaxial ducts are called “Pipe in Pipe * 'I PiP, that is, duct in a duct, in which an infernal duct conveys the fluid and an external euaxíal duct to the previous one, also called external enclosure, is in contact with and the environment , that is, water. The annular space between the two conduits can be filled with an insulating material or. yet, it doesn't contain any gans.

These systems have been developed to achieve a high level of thermal performance and specific versions have been developed to

2/27 respond in a way more adapted to large bottoms, that is, to withstand the pressure of the seabed. In effect, the water pressure being approximately 0.1 MPa, this is. core from 1 bar to 10 m deep, the pressure to which the duct must withstand is. then about 10 MPa, that is, 5 about 100 bar to 1000 m of depth and about 30 MPa. that is, about 300 bar to 3000 m.

These sets of coaxial ducts are manufactured by end-to-end assembly, by welding unitary extensions, hereinafter referred to as unitary elements of coaxial ducts, or 10 per montegem of coaxial duct sections, each section being itself constituted by a plurality of unitary elements of ducts, the length of which is. generally 10 to 100 meters, more particularly, about 12, 24 or 48 meters each.

Within the scope of the installation of sub-pipelines the great depth. these elements of unitary extension or these sections are manufactured on land. Then they are transported at sea on an installation vessel. At the time of installation, the unitary elements or sections of coaxial ducts are connected to each other on board the ship and as they are installed at sea. It is, therefore, important that this connection can be integrated into the method of assembling and joining the duct and installing it at the bottom of the sea.

For this purpose, generally use junction pieces or connection pieces forged in steel, joined to the ends of the said elements of the set of coaxial ducts to be assembled. The junction piece at the downstream end of a first coaxial duct assembly element is not yet connected by welding to the junction piece at the free end upstream of a second coaxial duct assembly element already assembled downstream.

These forged junction pieces are also intended to reinforce the re-sistence of the ducts subjected to considerable flexing during installation, especially in the connection area of two so-called successive unitary extensions and, more particularly, in the case of fun da-superflcie connections. çonfenr 'isna very high resistance to fatigue throughout the life of the installations.

In particular, said forged junction parts comprise two branches of revolution of which an outer branch and an inner branch forming a fork that delimits said annular space; the free cylindrical ends of the fork being directly mounted on the cylindrical ends, respectfully. external and internal conduits. Coaxial ducts and junction parts of this type have been described, in particular. in FR n ° 2873427 and GB n ° 2161565,

W in FR n ^to 2780713 and FR No. 2897919, described is another embodiment in which there is used a junction piece for securing and closing the annular space between the conduits) internal and external, at their ends, but the ends of the internal conduit are exceeded by those of the external conduit and by deformation of a terminal part of the external conduit around the terminal part of the internal conduit, in restriction of its diameter, until they approach each other to close the annular space, namely, pc-r welding the ends of the external and internal conduits together. This type of closing of the annular space and joining the ends of the coaxial cords is called "bending". Is it advantageous to have a welding machine access to the ends of the inner ducts of two elements of successive coaxial ducts beforehand? to weld them end to end without obstruction by the associated external ducts. The space between the ends of 2 external ducts of 2 elements of coaxial ducts mounted end to ex28 end is, in general, covered by a tubular sleeve that provides insulation and mechanically reinforces the level of the joint, namely, a sliding sleeve above the duct external.

The objective of the present invention is, therefore, to provide coaxial ducts of the PiP type, the sections or unit elements of the duct present in all their length, except at the ends, an extreme insulation howl due to the presence of an insulating material in the space between its internal and external ducts, in a preferable way.

4/27 associated with a forced operation of the formation of a vacuum to limit the phenomena of heat transmission by convection. On the other hand, when the howling of the ends of the refuted sections howled, the massive metallic connection between external duct and internal duct, by means of a so-called junction piece 5 or by winding, suppress any thermal insulation between the ambient melo, in general, water at 3 -5 * G at a great depth and the oil to be conveyed, in general, at a temperature of 40-45 X to 80-100 X or even more. Then, at the level of this junction zone by welding of the two so-called junction pieces or of the unit elements of coaxima “coiled” ducts, a particularly important thermal transfer, consequently, a loss of heat from the transported oil, which is at risk to cause paraffin stoppers or the formation of gas hydrates, if the temperature drops below 30-35 C at any point in the bottom-surface connection. Thus, the aim is to restore, at the level of 15 each of the junctions between sections, a sufficient level of insulation so that the oil is routed between the wellheads and the surface with a minimum of heat loss.

This thermal bridge problem is even more critical at the time of production interruptions, because the crude oil column is then stopped and if, in a main section of the section, the heat loss remains reduced, due to the resulting extreme insulation level of the PiP principle. it is not the same for connections between sections due to the thermal bridge thus created. In effect, a section of PiP with a unit length of 48 m showing an insulation level, in normal length, below 25 IW / mVK, has an average degraded value of 10-12% due to the thermal bridge existing in each of the ends, when said ends are not insulated. If the unit length is half, that is 24 m, the degradation due to the non-isolated ends is doubled, that is, 2025%. Also for sections with a length of 12 m. degradation 30 reaches, then. 40/50%, which, then, has little interesting PiP technology due to the complexity and considerable cost of its manufacture.

Here, the term "degraded average value" means the thermal loss

5/27 overall of the length of a section, including the parts of the junction or end-rolled zone at each of its two ends, divided by the length of said section.

Insulation means for the real external ducts5 are known to be present at high hydrostatic pressures and, therefore, suitable for use at high immersion depths, consisting of. '

- coatings in solid, substantially inoompressive materials based on polyurethane, polyethylene, polypropylene, etc., which are presented, if applicable, in the form of a solid tubular sleeve.

However, these materials have thermal conductivity and thermal insulation properties that are quite average, insufficient to avoid inconvenience in cases of interruption of production for underwater pipelines that carry hydrocarbons, or

- coatings in synthetic materials consisting of hollow spheres containing a gas and resistant to external pressure, immersed in binders, such as concrete, an epoxy resin, up to., whose thermal insulation properties are superior, but which are clearly more expensive and more difficult to install. In effect, semi-casings have been used which are assembled around the joint weld to be protected and after completion of the same

In addition, insulating materials with superior thermal insulation properties are known, that is, with less thermal conductivity, reinforced, in certain cases, with phase-changing properties, in particular, in the form of the gel.

Such materials have been described, namely, in the patents FR m-2800915, FR No. 2820426. FR No. 282D752. No WO 2004/003424 and No. WO 00/40886. However, these insulating gels, due to their insufficient mechanical behavior and the fact that they are obtained from physical and chemical reactions, physico-chemical between different components, are injected

The liquid sub-form, immediately after mixing the different components, and inserted or injected between said external and internal conduits of the set of coaxial conduits of type Rpe-m-Pípe.

tVZ /

Mecânico the mechanical behavior of these gels is insufficient to withstand, by itself, the mechanical stresses of the ducts based on the seabed and are not used outside the external ducts of the P / p & ~ ^ -P / pe duct set, È that is why they are not adapted to isolate the junction zones of two PiP duct sections assembled end to end by welding and, possibly, by means of revolution joint pieces.

WO n ^í! 2008 / 05325l describes different means of insulating a thermal insulation sleeve from the junction zone between the two unitary duct elements, said thermal insulation sleeve consisting of steel PiP ducts joined at their longitudinal ends by winding and whose annular space contains a thermal insulation material.

In WO n ^f! 2008 / D53251. in figures 3 and 4, the internal volume between the two walls of the sleeve is partially filled, nor an insulating material (see page 13, lines 14 to 22) and partially filled with gas, such as air.

In this document, page 13, line 20, it is stated that the steel F / p and Pipo structure that ensures the insulation of the junction zone is expensive and heavy. That is why, in this document, an improvement to the insulation system described in figure 5 is proposed, replacing the sleeve with a lighter casing with a single steel duct element (see page 18, lines 28 and following), which it is covered with multi-layered insulation (see page 19, lines 5 and following) in expanded polypropylene foam or synthetic pohurethane foam.

But this steel sleeve is inefficient in terms of thermal insulation taking into account the high thermal conductivity of açu,

The object of the present invention is, therefore, to provide improved thermal insulation devices at the level of joints by welding coaxial unit conduit elements connected end to end.

To this end, the present invention provides a set of two coaxial conduits of the PIP type, comprising at least two unitary elements of coaxial conduits, each comprising an internal conduit and an external conduit with an annular space, preferably , filled with an exempting material, assembled end to end by welding, faced because it comprises a hollow tubular wall sleeve in rigid or semi-rigid material, in plastic or composite material ·, involving the said duct in front of the welding junction of the two said unitary elements of coaxial ducts, said hollow tubular wall of the sleeve comprising an outer shell and an inner shell connected at its longitudinal ends in a watertight manner, thus defining an inner volume filled with a practically incompressible thermal insulating material.

This hollow tubular wall of said insulation sleeve is particularly advantageous because it allows the use of insulating products which, otherwise. ships would behave sufficiently to withstand the mechanical stresses of the pipelines based on the seabed, with high thermal insulation properties. In particular, this hollow tubular wall allows thermal insulating gels to be packed inside, which have the advantage of preventing the convection phenomena inside the insulating mass, on the one hand, and, on the other hand, from being obtained from physical, chemical reactions or physico-chemical between different components, which makes it possible to inject them in liquid form immediately after mixing the different components, and the integral filling of the hollow tubular wall can be effected before the mass gelation begins significantly.

Because the insulating material is practically compressible, that is, among other things, it does not contain gas, the rigid or semi-rigid material of the hollow tubular wall of the sleeve, subjected to hydrostatic pressure at great depth, is supported by said insulating material. , so that said rigid material or sieve of the tubular wall of the sleeve does not require mechanical strength as high as that of a steel duct.

.... .... .......................

8/27

The insulation sleeve according to the invention does not comprise any steel element. but its rigidity as a whole, due to said practically incompressible insulating material, is sufficient to maintain a stable cylindrical shape at the moment of its handling and at the moment of its final installation in the duct to be isolated.

Here, sserni-rigido is understood. » a material sufficiently rigid to maintain its shape despite the weight of the insulating material contained in the sleeve, but nevertheless presenting a certain flexibility to accept deformations, namely, to follow deformations resulting from the change in volume of the material at the time of its eventual change phase.

By "tubular wall", it is understood that said outer and inner sheaths may have a cross-sectional section perpandsoular to the longitudinal XX * axis of said sleeve in a circular or oval shape or even polygonal.

Oval or polygonal shapes are particularly suitable if the virtually compressible insulating material is a phase-changing material, so that the walls can thus deform to withstand the swelling at the time of the material's phase change, if 20 where applicable, as described in WO No. 2OO4 / O03424.

This hollow tubular wall is also particularly interesting in that it prevents the eventual longitudinal migration of the virtually compressive insulating material! that it confines.

It is understood that said insulating material is incompressive!

has a thermal conductivity lower than that of the material constituting the aforementioned inner and outer casings of the tubular wall with said sleeve

The installation of insulation sleeves in each of the connections gives a significant gain to the average insulation of a section and the 30 degraded average values previously defined are. then, respectively, on the order of 7-8% for a 48 m section, 14-18% for a 24 m section and 28-36% for a 12 m section.

On the other hand, in the production interruption room, the performances will be the same for each unit length of the section, because then the cooling phenomenon is mainly located at the level of thermal bridges, that is, at the level each of the connections between sections, respectively. all 48-50 rn, all 24-25 m or all 12 m.

Preferably, said practically incompressible thermal insulating material is a phase change insulating gel (PCM),

Preferably, the insulating gel comprises a first compound having thermal insulating properties, such as alkanes, comprising a hydrocarbon chain with. at least six carbon atoms, preferably at least ten carbon atoms, in admixture with a second compound consisting of a gelling or structural effect polymer compound. namely, by retioulaçãu, such as a polyurethane, palipropylene, piethylene or silicone type compound, said first compound, of a preferred fear, in the form of particles or microcapsules dispersed in a matrix of said second gelatinized or reticulated compound, confining said matrix, thus, said first insulating compound,

These insulating gels have the interest of being able to be used in a liquid state and transform, after a few hours, into a gel. in which α insulating compound is found to be encapsulated in a matrix of the second compound that plays, to a certain extent, the role of a sponge capable of confining the insulating material and keeping it in a form of substantially constant thickness, thus radically reducing convection phenomena and, if necessary, absorb volume variations if the insulating material is a phase-changing material.

More particularly, said first compound having thermal insulating properties can be a phase-changing insulating material, namely, alkanes or alcohols having a hydrocarbon chain with, at least, fourteen carbon atoms, such as paraffins, ceres, bitumen, tar, fatty aloools or ghcóis

In this case, the second gelling compound can absorb an important part of the volume changes of the first compound at the time of the phase changes.

These phase-changing insulating materials are advantageous because they behave like heat accumulators capable of restoring their energy in their solidification phase and, conversely, able to absorb this energy during melting. When they restore the accumulated energy, these materials therefore allow to increase the duration of production interruptions without risk of duct comatting by premature cooling 10 of their content,

The phase change material advantageously has a liquid / solid melting temperature between 20 and 80 '' C. higher than the temperature h from which the fluid circulating inside the conduit shows an increase in viscosity harmful to its circuit? in the duct and below the temperature tj of the fluid circulating in the duct in operation.

More particularly, the phase-shifting insulating material comprises chemical compounds of the African family, preferably a long hydrocarbon chain with at least. 14 carbon atoms, such as paraffin. More particularly, it is Heptacosane with the formula having a melting temperature of about 50 ° C.

These are compounds that combine the thermal insulation properties with the fact that they maintain a change temperature of 28 phases during the entire period of their phase change, thus delaying the cooling of the inner space of the sleeve, namely, oil conveyed by the PiP conduct, namely, in the case of production interruption;

In a particular embodiment, said insulating gel is a mixture of kerosene and polyurethane.

Kerosene is mostly constituted by an alkane with a carbon chain with at least ten carbon atoms and no phase change properties.

Insulating gels of this type have the following physicochemical characteristics.

- consist of an insulating compound. of change in fa5 if, if not, dispersed in a retayed matrix forming a sponge with microscopic and watertight hollow cells, the matrix is either physical or chemical, or even physical-chemical, producing the referred cross-linking after several hours, at ordinary temperature (10-25 X) or by heating the ounce, the gels thus obtained have a Shore A20 to A8Q hardness according to the type of matrix.

its thermal conductivity ranges from 0.130 to 5.150 W / m.XK

Advantageously, at least said inner shell or preferably at least said outer shell of said sleeve forms a single piece with connecting elements at its longitudinal ends, able to close the space between the duls hell and outer casings of the hollow tubular wall of the sleeve at its end, said piece being made of thermoplastic material with a reduced thickness of less than 20 mm, preferably with a thickness of about 4 to 8 mm.

obtained by rotational molding, such as polyethylene, polypropylene, polyamide or PVDF, in particular and said piece is attached to the other outer or, respectively, inner shell of the hollow tubular wall of the said connecting elements,

Preferably, said part obtained by rotational molding comprising said inner shell or. preferably, the outer of the sleeve with said end connection elements comprises at the level of said inner shell or, preferably, outer shell of the sleeve, convex or rounded or serrated concave grooves or grooves.

It is understood that these grooves form locally, over a distance of 1 to 10 cm in the length of the sleeve, variations in diameter of said envelope from 0.5 to 5 cm, preferably, regularly spaced throughout the length of the sleeve. sleeve, which contributes to make the tubular wall of said sleeve more rigid and to compensate for its reduced thickness resulting from its method of obtaining by molding by rotation.

More particularly, one of said inner or outer sheaths of said sleeve integral with said end connecting elements is obtained by rotational molding, the other outer or respectively inner shell of the sleeve being obtained by extrusion or by rotation molding and being fixed by gluing or welding to said connecting elements.

In the case where said other casing is obtained by extrusion, it does not have said grooves or corrugations and, in the case where it is obtained by rotational molding, it can comprise these corrugations or grooves.

Even more particularly, said hollow tubular wall comprising said inner and outer sheaths and said end connection elements, is obtained in the form of a single munobloc piece by rotational molding, preferably having the inner shell , a slightly tapered shape and devoid of the said undulations or grooves, in order to allow its dewatering.

In an advantageous embodiment, said inner casing of said hollow tubular wall of the sleeve comprises an average zuna of greater diameter than the end zones adjacent to it on one side and the other, thus forming a concave part in which it is located. housed, at least, by a first waterproof pouch involving the said set of coaxial ducts along its entire periphery, filled with a non-isolating phase change material, of a preferred mute, a molten salt, the thickness of the pouch being thus preferably filled less than the thickness of said concave part, preferably still from 1 to 10 cm.

The concave delivery in said inferno wrapper allows to keep said bag in place avoiding any longitudinal displacement and maintaining, on one side and the other of the bag, a maximum thickness of said sleeve.

The phase change material is advantageously present. a liquid / solid melting temperature comprised between 20 and 80 ° C. above the temperature P from which the fluid circulating inside the conduit shows an increase in viscosity detrimental to its circulation in the conduit and below the temperature t ₂ of fluid circulating in the conduit in operation.

Such rafts are placed near the set of coaxials conduits ₅ and preferably are not in contact with this diretameiile. Does this space between the PCM material and the ducts make it possible to reduce the caloric absorption speed of oil in the process of restarting production, after an interruption, so that the oil maintains the temperature in the bush? possible time and only reach the value ty when it is close enough to the surface to reach it without the temperature dropping below the temperature b at which some of its components freeze, thus preventing its circulation in the duct.

Insofar as the sleeve contains a substantially inexpressible insulating material, the PCM material included in said inner pouch is not. necessarily, a material with poor thermal conductivity. In the case of melted PCM material, the latter have, in general, a high thermal conductivity.

The position of the phase change material closest to the set of coaxial ducts optimizes these properties located in the zone where it is most effective, that is, essentially located in the vicinity of the duct, because only the PCM material next to the hot duct can accumulate heat at the moment of its liquefaction, r> PCM material too close to the marine environment, having, in general, the seabed temperature, that is, 4 '' C would not participate in the heat accumulation process; it would always remain solid or crystallized, which would therefore be harmful.

· * ·

14/27

Still in an advantageous fashion, said outer casing of the tubular wall of the sleeve comprises an average part of a larger diameter than the end zones adjacent to it, in front of the said average zone of greater diameter of said inner casing, in order to maintain a thickness of graphically incompressible insulating material within the envelope of said middle zone, substantially constant throughout the length of said sleeve.

It is understood that the outward growth of the larger diameter medical part of the outer shell therefore aims to compensate the concave part of the inner shell in order to conserve a thickness of thermal insulating material contained between said inner and outer shell substantially constant and therefore a constant insulation over the entire length of said sleeve.

Even more advantageously, said sleeve further comprises a material; filler filling the space or gap between said inner casing of the tubular wall of the sleeve and said external conduit or, if applicable, internal conduit of the set of coaxial ducts, said filling material ensuring the connection of said sleeve to the set of coaxial ducts, preferably a hardenable filling material of the resin or cement type, preferably still a thermal insulating material,

According to other embodiments, the sleeve can be fixed to said external conduits by means of end joint joints and / or wedges and / or mechanical strapping means, with or without said filling material.

In one embodiment, each of said unitary elements of the combined coaxial ducts comprises, at its end, a revolution joint piece connected to said internal and external ducts at one end of the revolution joint piece and having the two pieces of revolution revolution joint assembled by welding at each other, at its other end, said sleeve being centered in front of the joint weld between the two revolution joint pieces and

15/27 extended beyond the connection welds between said junction parts and each of said unitary elements of said coaxial conduits.

More particularly, each said coaxial unit unit element comprises, at its end, said unit piece, the two unit parts being connected by welding between them and comprising one of said unit parts, on its external surface, one protuberance in the form of a stop or collar capable of allowing the retention in suspension of the unitary duct element of coaxial ducts that is connected to it when it is in the vertical or inclined position. from an installation vessel at sea and said tubular sleeve comprises an end zone with an inner casing of a diameter greater than that of the opposite end in the longitudinal direction, covering said end zoon of the inner casing of greater diameter the set of 15 coaxial conduits within said sleeve, at least from said protuberance or collar.

It is understood that the difference in diameter between the two inner shell end zones is greater than the thickness of said protuberance or collar. This feature allows the sleeve to be pushed over 20 of the coaxial ducts set close to the external duct, in the area upstream of the said protuberance or collar.

According to another variant, each unitary element of coaxial ducts comprises an outer duct end retracted in relation to the inner duct end, the annular space between said external and internal ducts being closed by enrollments, consisting of the deformation of the terminal part of the external duct whose end is connected directly to the surface of the internal duct, in a preferred way, by welding and the two unitary elements of coaxial ducts are assembled by welding each other at the level of the ends of their internal ducts, extending if said sleeve for a distance of at least 50 cm, preferably less skin. 1 m above those external conduits, in addition to the welds

16/27 bearing and the space between the inner casing of said sleeve and the internal conduit of the coaxial ducts as a whole between the two weldings is filled with an insulating material, preferably a phase change compound, of a still more preferred, a molten salt contained, skin less, in a second watertight pouch completely surrounding said inner conduit, the longitudinal end of said pouches having preferably, in axial longitudinal section, a beveled profile in order to fit more closely to said external conduit after the winding zone between said external conduit and said inner shell of said sleeve.

Advantageously, said sleeve contains said first and / or second pockets, each being formed by two semicylindrical pockets diametrically opposed on one side and the other of said set of oaxial ducts

Thus, said first and second bags are easier to place inside said sleeve.

More particularly, the greeting of said sleeve is comprised between 1 to 10 m, in a preferred fashion, from 2 to 6 m. preferably, with a sleeve thickness of 5 to 25 cm, preferably still having said inner and outer casings of the tubular wall of the sleeve a wall thickness of 2 to 10 mm.

The thickness of the sleeve extends over the distance between said inner and outer shells including the thicknesses of said inner and outer shells.

Thus, the sleeve extends for 1 to 3 m on one side s of the other side of the welding joint and, therefore, covers, if necessary, the connected connecting pieces and a part of the unitary elements of assembled coaxial ducts in said bare junction parts, if applicable, covers the gap between the winding points between said external ducts and internal ducts of the unit elements of coaxial ducts mounted at the level of the ends of their internal ducts, as described below.

The present invention also provides a hollow tubular wall insulation sleeve filled with a virtually incompressible thermal insulating material

Other features and advantages of the present invention will appear in view of the detailed description that follows, using the following figures, in which '

- figures IA and IR represent an insulation sleeve according to the invention, respectively, in a side view and in a longitudinal north side view,

figure 2A is a perspective view of the rotational molding process of an insulating sleeve,

- Figure 2B is a side view of an insulating sleeve during filling with gel-type insulating compound,

figure 3 is a section in side view of an insulating sleeve 15 showing an internal bag filled with phase change material,

- figures 3A to 3B are sectioned according to the XX plane of figure 3, allowing two embodiments of said internal bag filled with phase change material,

- figure 4A is a section in side view, detailing the assembly of an internal truffle inside an external casing obtained by rotation molding to form an insulating sleeve,

- figures 4El & 4G standardize a method of assembly by hot air welding of the inner tube to the outer shell pre-assembled in .25 according to the mode defined in. figure 4A _S

- Figure 5A represents, luckily and in a side view, the ends of two PiP-type sections assembled by means of forged parts, the whole being surrounded by an insulation sleeve according to the invention,

- Figure 58 represents, in cross-section and in side view, the ends of two PiP-type sections assembled using forged parts, one of which has an external excrescence which serves as support when installing at sea from an installation vessel in J. the assembly being surrounded by an insulating sleeve according to the invention, with a part comprising a larger internal diameter,

- figure 6A represents, in the north and in a side view, the ends of two traces of PiF tip mounted by «winding», surrounded by two pockets in the form of semi-shells of phase change material, the whole being involved by an insulating sleeve according to the invention, (the insulating sleeve not shown in the upper part of the figure above the longitudinal axis ZZ).

Figure 68 represents in cross section the two bags filled with phase change material,

- figure 7 is a side view of an installation vessel equipped with a J installation tower.

figures 8A and 8B detail, in outline and in side view, the mounting on board of the ship in figure 7. of an additional section, respectively in the welding phase, and ,. then, in the phase of ring filling after the sleeve according to the invention has been lowered to its final position,

- Figures 9A and 98 represent, in short and in side view, outer casings 1a and inner 1b cylindrical with circular cross-section obtained by extrusion and assembled at their longitudinal ends by ring collars 1c.

Figure 18 represents, in section and in side view, a thermal insulation sleeve 1 with a hollow tubular wall comprising a double wall 25 consisting of an outer shell 1a and an inner shell 1b connected together by each of its ends 1c. the set defining a watertight 1d volume intended to be filled by a graphically incompressible insulating compound, preferably a gel, preferably still a phase change gel capable of restoring calories> to the PiP type conduit around which said sleeve is arranged.

In order to ensure dimensional stability of the outer casing at the time of the manufacturing process and during manipulations at the local level, the outer casing has an advantageous pattern, concave serrated grooves 2 or 2b or convex circular grooves 2b, extended transversely to the / 2 'direction. axial longitudinal of the wall sleeve Ia, with a width of 1 to 5 cm in the longitudinal ZZ 'direction spaced evenly or not, for example, from 20-30 cm to 20-30 cm.

Said insulating sleeve is preferably obtained by rotational molding in one operation. In figure 2A _: in perspective, the principle of jacketing by rotation grinding, known to the person skilled in the art, represented, which consists of rotating, in space, in general in a pseudo random way, according to two axes 3a, 3b, a mold of the form, generally metallic, in which granules of thermoplastic material, such as polyethylene, polypropylene, polyamide or PVDF, have been introduced and which is gradually heated, for example in an oven, to a temperature at which the granules reach their temperature fusion The fused granules then stick to the mold wall and, due to the fact that the mold is pseudo-random rotating along two axes, the wall thickness grows substantially uniformly over the entire internal surface of the mold, When all the granules they are molten, the rotation is continued and the external wall of the connection part that serves as a mold is cooled, in the free air, or by spraying water. When the mold is cold, the mold is opened and the molded part is refined by rotation, making the demolding of the external part, in general, without difficulties, because the thermoplastic material presents a retraction of 0.5 to 2% according to the material. On the other hand, to facilitate the demoulding of the part of the mold in contact with the inner casing 1b, the said inner mold is advantageously manufactured in two parts, left and right, each part being advantageously, conically profiled 3c. as detailed in figure 18, ο which allows the extraction of each of the aforementioned parts, the left part to the left and the right part to the right, being the advantage, from 1 to 3% advantageously, therefore presenting the inner shell 1b a biconic profile with a retraction of its internal diameter in its central 3d part and two symmetrical inverted conical parts on one side and the other. The

20/27 enclosures 1a, 1b outer and inner have a thickness of 5-5 mm.

After demolding, bed represented in figure 2B_. the interior Id of said sleeve 1 is filled with a practically inoompressible insulating compound 4 from an openable opening 4a. Said insulating compound, preferably a gel-like mute. it is transferred, advantageously, to the liquid stay until the complete filling of said volume 1d. then, the filling hole is permanently and perfectly sealed. For example, a polyurethane-kerosene gel from the ARKEMA Company (France) is used, which is transferred to the liquid state after mixing the components and which retinulates cold in a few hours.

The insulation sleeve 1 is intended to isolate the connection zone of two sections 5a-5b of type PiP conduits, as shown in figures 5A, 5B, 6A and 811

In figure 5A. The assembly of two sections at the two-piece level 9a, 9b of forged revolution joints, as described in FR 0 ^ 2973427, was represented in side view and side view. Each section consists of an external 5ai-5bl duct. cylindrical, coaxially involving a cylindrical internal 5a2 ~ 5b2 conduit, the external Sat-bbl conduit being sealed, in a sealed manner, in 8a, to a piece touched, the sealed itself, in a sealed manner, in 8b. to the internal conduit 5a2-5b2, to constitute a volume 5a3 filled with insulating material, preferably under reduced gas pressure, for example, as described in FR No. 2878Ô36. The two sections are assembled by welding in 7, on board the J installation tower 21 installed on the installation ship 20, as illustrated in figure 7,

The stretches 5 have a length of about 12, 24 or 48 m and present in all their length, except in the extremities, an extreme isolation level due to the presence of an insulating material, in a desired way, associated with a formation operation forced vacuum to limit the phenomena of heat transmission through observation. On the other hand, at the ends of the referred sections connected between ethes, the massive metallic connection between the two sections puts the environment in direct contact, in general, water at 3-5 X at very great depth and the oil to be conveyed, in Generally, at a temperature of 40-45 X to 80-100 X. or even more, it then follows thermal transfer and, consequently, a loss of heat from the oil transported, which can generate paraffin stoppers. o the formation of gas hydrates, if the temperature drops below 30-35 X at any point in the bottom-soperflcie connection. Thus, it is sought to restore, locally, at the level of each of the junctions between sections, a sufficient level of insulation so that the routing of oil 10 between the wellheads and the surface is done with a minimum of heat loss.

This thermal bridge problem is even more critical at the time of production interruptions, since the crude oil column is then stopped and if in its main section of the section the heat loss remains reduced, due to the level of extreme insulation resulting from the principle of PiP, this no longer happens in front of the connections between sections due to the thermal bridge thus created. In effect, a section of PiP with a unitary extension of 48 m showing a level of insulation, in normal length, called tPvafue. less than 1 W / mÕK, has its average value degraded by 20 10-12% due to the thermal bridge existing at each of the ends, when those ends are not isolated, if the umtary extension is half, or sep 24 m, the degradation due to non-isolated ends is doubled, that is, 20-25%. The same thing happens with sections of length 12 m, the degradation then reaches 40/50%, which then makes the PiP technology unattractive due to the complexity and the considerable cost of its manufacture,

The installation of insulation sleeves in each of the connections gives a significant gain to the average insulation of a section and the previously defined average degraded values are, therefore, in the order of 7-8% respectively for a section of 48 m. 14-1835 for a 24 m section and 28 -36% for a 12 m section.

On the other hand, in the case of interruption of production,

22/27 performances will be the same for each of the unitary stretches, therefore the cooling phenomenon is mainly located at the level of thermal bridges, that is, at the level of each connection between strokes, respectively. all 48-50 m, all 24-2-5 m or 5 all 12 m.

For example, a non-insulated joint creates, in the event of production interruption, for example, in the event of an incident on board the FPSO, a PiP consisting of an internal duct 300 mm in diameter and an external duct 400 mm , delivering crude oil at 65 C, a temperature drop of 48 ^and C in 4-6 hours, while this junction isolated by a sleeve injected from the insulating gel will see this temperature drop over a period of more than 24 hours. If. in addition, an internal pouch 22, described below, comprising a phase-changing compound, such as a molten salt, is added, then the same temperature drop will be achieved only after 30 to 36 hours, which limits, thus, radically, the risks of formation of paraffin or gas hydrate and thus leaves more time to repair and relaunch production,

The insulating sleeve, according to the invention, is superimposed over each of said welding joints 7 between sections, with said sleeve having a thickness of insulating material in said hollow wall from 10 to 30 am and extending said sleeve, preferably on one side and the other, of said joint over a length of more than 1 m, preferably of a length of 1.5 m to 3 m, that is, if applicable In addition, above the external ducts 1a to a25, there are parts 9a, 9b of junction or welding. 6a, 6b of winding closure described below,

In figure 6A, in the north and in the side view, the assembly of two 'rolled' strands is shown. Each of the sections consists of an external tubular housing 5a1-5b1 involving, in a coaxial mute, an internal 5a2-5b2 duct, the external housing 5a1-5b1 being "rolled up" at each of its ends, and paid off, in order tight, at 6a <6b, to the 5a2 ~ 5b2 duct. internal, to constitute a volume 5a3-5b3 filled with Isotent material, preferably under reduced gas pressure. The space 5a4 between the Internal duct not covered by the external duct and the sleeve is filled, in an advantageous way, by watertight bags containing a phase change compound, said compound being, in particular, a molten salt. bag is advantageously cylindrical, constituted by two bags 20a, 20b of semicircular section disposed diametrically opposite each other, such as shown in the transverse cone? 613, in such a way that the duct is covered by two identical rafts 20a 20b, with the right and left ends, according to the ZZ axis, 10 advantageously, profiled 20c to attest as close as possible to the external duct 1a in the zone between the outer conduit and the inner wall of the sleeve, in addition to the weldings 6a, 6b of winding. Thus, a maximum bag volume and, therefore, heat capacity are provided.

In a preferred version of the invention shown in figure 3, the insulating sleeve 1 comprises, in the middle, and inside its internal face 1b, a recess 21 into which, advantageously, a pouch 22 containing said material phase change, the thickness of which from 1 to 5nm is such that, after being columned inside the insulating sleeve, its internal diameter is slightly larger than the internal diameter of the internal wall 1b of said sleeve on one side and the other of the concave corner 21. To facilitate installation within said insulating sleeve, advantageously two semicircles 22a, 22b of semicircular placement are arranged diametrically opposed to each other, as shown in figure 3A, or even a single pouch opened according to generatrix 22c, as shown in figure 3B, which can be folded over itself to be more easily inserted into the concave housing 21.

In a preferred version of the invention, the insulating sleeve is manufactured in two stages, as shown in figures 4A, 48A 4C. In spite of this, the outer casing 1a is rotationally molded in a known manner, said outer casing comprising reinforced ends 1c 1e, that is, greater in thickness than the main section, having said thickness 524/237 mm. Next, an inner casing consisting of a smooth tube th obtained, for example, by continuous trusion is inserted into said outer casing, and then cut to length so that the length of said tube matches the length of the casing la exit suit, as shown in figure 4A, Once the insertion is complete, the end 1e of the outer shell 1a and the said inner tube 1b, for example, of a molten shell, by welding 26 in hot air or under atmosphere, are solisized. of neutral gas, such as nitrogen, in order to seal the hollow wall of the insulation sleeve in order to fill it with an insulating gel 4.

In figures 8A-8B, in section and in side view, the installation phase of a sleeve in a J installation tower 21 of an installation ship 20, at the level of the junction between two sections 5a-5b, such as as defined using figure 5B. The conduit 5a in suspension is kept in the 15 installation turret in J due to shah gala 30 located on the periphery of the forged part 9a. The section 5b, on which the sleeve 1 has previously been installed in a retracted position, that is, removed from the assembly area by welding, is then brought into contact with said duct 5a in suspension e. then. settled by an orbital welding device 31. After con- trotting and finishing operations, the sleeve is lowered by axial sliding according to ZZ. 'So as to overlap said weld 7, in a preferred way, at an equal distance from its ends. The lower end of said sleeve cooperates with a gasket, of a preferred made, an O-ring 32 pre-installed in the lower suspension section 5a. Thus, the space 25 or gap 33 within the sleeve, that is, between the inner shell of the sleeve and the said pockets 20,22 and the coaxial conduit set 5a, 5b, can be filled (a) with a compound 34 adherent filler that allows the sleeve or the set of coaxial ducts to be attached, preferably a practically iricompressible insulating material, filling from the upper end of said sleeve. Compound 34 can be a peliurethane resin, loaded or not with glass microspheres to then constitute an insulating complement to the sleeve, or

25/27 an Insulating gel or an aqueous gel or an ice comprising a phase change material.

In figure 5B, because the section 5a comprises a collar 30, said sleeve advantageously has, on its lower part, an inner diameter 35a greater than the inner diameter 35b of the upper part, said diameter 35a being slightly higher to the outside diameter of said gc-la 30. This makes it possible to minimize the amount of filler in the upper part of the anima sleeve of gluttony 30 and, in certain cases, to minimize the thermal areas with the outside.

In figures 9A and 913, a variant of embodiment has been shown in which the outer shells 1a and the inner sheath 1b of the sleeve have a straight cylindrical shape and are obtained by extrusion. both, for example, in polyblue and whose longitudinal ends are connected by welding of ring collars inserted between said inner casings 1b and outer 1a at their ends and paid off using an instrument 2.6 previously described.

In figures 5A and 5B, the two sections ba, 5b comprise nothing, a joint piece 9a, 9b mounted on each other. Each said joint piece 9a, 9b is a revolution joint piece delimited as follows:

«In a radial direction in relation to a longitudinal axis XX 'of revolution of the said part, this is delimited by a cylindrical internal wall substantially the same diameter as that of the main section of said internal 5a>, 5b- <duct and by an external cylindrical wall with a diameter substantially equal to the external diameter of the main section of said conduit 5a <-5b _; external, and • in the longitudinal axial ZZ ¹ direction, * on the side of said joint piece assembled by welding 8a to the end of said external and internal conduits of said unitary element of a joint of, through the menus, two coaxial conduits, said external and internal walls of said junction form, in longitudinal section, first branches, respectively, external 13 _; and internal

2/26?

13? with, substantially, the same thickness as the external ducts 5a e and internal ducts 5b- _: on which they are mounted, delimiting said first external 13 <and internal 13 branches? a first annular cavity 14

14 .. and * on the opposite side of said junction piece mounted on another said junction piece, itself assembled by welding 8a, 8b at the end of said other unitary element of a set of two coaxial ducts, said outer and inner walls form , in longitudinal section, second branches, respectively, external 15 <and internal 15?, delimiting a second annular cavity 16, * the two said first and second joining pieces being welded to each other only at the end of said second branches 15; external, * the ends of said two branches 15? internal non solid data come into contact with each other, so that said second internal cavities 16 are not watertight with respect to the interior of said internal wall and said internal conduit, and * the bottoms of said first and second cavities 14 , 16 are spaced in said longitudinal ZZ 'direction, in order to delimit a massive full zedge of said junction piece in which said outer and inner walls form the outer and inner faces of the same cylindrical wall and the bottoms of said first and second cavities 14. 16 are spaced at least 0.5 times the maximum wall thickness of said joint piece, preferably greater than said maximum thickness.

Said second internal cavities are intended to be filled with the same fluid that circulates in the internal conduit.

The point of contact between the free ends of the second inner branches of the two junction pieces mounted on each other ensures an almost continuity of the internal conduit and allows to avoid vortex turbulence phenomena in the circulation of the lower naked fluid of the conduit set at the level connection of the two junction pieces.

On the other hand, the fact that two adjacent junction pieces are welded only at the end of said second outer branches, allows the totality of the load and stress transfer phenomena to be located at the external level and does not imply said internal walls , which allows better control of the risks of cracking or tiredness phenomena and prevents the device from being completely ruined at the level of the inner wall,

In addition, the fact that the two ends of the said second inner branches of the two adjacent pieces, according to the invention, are not welded together, allows minor movements of said inner walls face to face due to possible flexions or pressure variations or temperature and allows the said internal walls to be plastically deformed and allow the sealing of said second internal branches without running the risk of transferring loads with contact pressure, which allows to avoid disturbing the distribution of stresses in the assembly area and that the essential of the tensions is returned to the level of the external walls of the referred parts.

Lastly, the massive filled zone between the bottoms of the first and second cavities allows to transfer the compression or traction efforts between the internal and external ducts.

All of these characteristics contribute to radically improve the behavior in flexion, as well as in fatigue, of a device involving two elements of coaxial set equipped with the said junction parts and connected to each other, on board installation ships.

Claims (10)

1. A set of two coaxial ducts of type PiP, comprising at least two unitary elements (5a, 5b) of coaxial ducts comprising, silk, an internal duct (5a -,>, 5b?) And a duct (5a? < 5b ',) external with a ring space (53 ^, 5M ring, in a desired way, filled with an isoard material, assembled end to end by welding, characterized by comprising a sleeve (1) of hollow tubular wall in rigid material or semi-rigid, preferably plastic or composite material, involving said duct in front of the zone (7) of 10 welding junction of the two said elements (5a, 5b) unitary of coaxial ducts, said hollow tubular wall of the sleeve comprising an outer shell (1a) and an inner shell (1b) connected at its longitudinal ends (1c) in a watertight manner thus defining an internal volume entirely filled with a thermally incompressible thermal insulating material. consisting of an insulating gel, 2. Set of two ooaxial ducts of type PiP, according to claim 1. characterized in that the said thermally incompressible thermal insulating material is a phase-changing insulating gel (PCM). 3. Set of coaxial ducts, according to the claim 20 1 or 2, characterized in that at least said inner shell or preferably at least said outer shell (1a, 1b) of said sleeve forms a single piece with connecting elements (1c) at its ends longitudinal, able to close the space between the two inner and outer casings of the hollow tubular wall of the sleeve at its end, having the 25 said piece (la-lc) in icoplastic material a reduced thickness, less than 10 mm, preferably a thickness of about 4 to 8 mm, obtained by molding for rotation and said piece (1a-1c) being fixed to the other external or, respectively, inner casing of the hollow tubular wall of the sleeve at the level of said elements (1c) of connection. 4. A set of coaxial duct elements, according to claim 3, characterized in that said part (1a, 1c) obtained by molding for rotation comprising a retaining inner or, intentionally, outer casing of the sleeve with said end connection elements (1c) comprise, at the level of said inner shell or _; preferably, outer sleeve housing, rounded or serrated (2) or concave (2a) or concave (2b) grooves. A set of coaxial ducts, according to one of claims 3 or 4, characterized in that one of said inner or outer sheaths of said sleeve attached to said end connection elements (1c) is obtained by rotational molding, the other outer or, respectively, inner shell of the sleeve obtained by extrusion or by molding by rotation and being fixed by gluing or welding to the said elements (1c) of the connection, A set of coaxial ducts according to one of claims 1 to 4 _S, characterized in that said hollow tubular wall comprising said inner and outer shells (1a. 1b) and said strands (1c) of. end connection is obtained in the form of a single monoblock piece, the inner shell preferably having a slightly conical shape (3c) and devoid of the said undulations or grooves, in order to allow its demoulding. Coaxial duct assembly according to one of claims 1 to 6, characterized in that said inner casing (1b) of said hollow tubular wall of the sleeve (1) comprises an average corner of a larger diameter than the end zones that it has they are adjacent on one side and the other, thus forming a concave part (21) in which at least one watertight first pouch (22) surrounds said set of coaxial conduits throughout its periphery, filled with sound a non-insulating phase-changing material, preferably a molten salt, the thickness of the pocket thus filled, preferably being less than the thickness of said concave part, preferably still from 1 to 10 cm . Ooaxial conduit set according to claim 7, characterized in that said outer casing (Ia) of the tubular wall of the sleeve comprises an average part of a larger diameter than the adjacent end zones, in front of said zone (21) medium of greater diameter of said inner wrapping, in order to maintain a thickness of substantially uncompressing insulating material inside the wrapper in said zed (21) inner. substantially constant throughout the length of said sleeve. A set of coaxial duct elements according to any one of claims 1 to 8 _: characterized in that said sleeve further comprises a filling material (33), filling the space or gap between said inner shell (1b) of the tubular wall of the sleeve 10 and said ext.ema conduit (5ai, 5b J or if applicable, internal conduit of the coaxial conduit set, the said filling material ensuring the connection of said sleeve to the coaxial conduit set, in a way Preferably, a resin or cement type hardenable filler, in a still preferred fashion, a thermal insulating material. Coaxial duct assembly according to one of Claims 1 to 3, characterized in that each of the said unitary elements (5a. 5b) of the coaxial duct assembly is assembled with a piece (9a, 9b at its end) ) of revolution junction connected to said internal and external conduits at one end of the junction piece 20 of revolution a being the two revolution junction puddles assembled by welding at each other at its other end, said sleeve being centered in front of the welding of junction (7) between the two pieces (9a, 9b) of revolutionary junction and extending beyond the connection welds (Ba. 8b) between said junction pieces and each of said 25 unit elements of the assembly said coaxial conduits. 11. The coaxial duct assembly according to one of claims 1 to 9, characterized in that each said coaxial duct element (5a, 5b) comprises an external duct end retracted in relation to the internal duct end, being α space ( $ 5a. 30 5bs) annular between said external and internal ducts closed by winding (6a, 6b), consisting of the deformation of the terminal part of the external duct whose end is directly cannulated to the surface of the internal duct (5¾ 5b?), Preferably by welding, and the two unitary elements of coaxial ducts are assembled by welding (7) one to the nut at the level of the ends of their infernal ducts, the said sleeve extending (1> for a distance of at least 50 om, preferably, at least 1 m „above said ducts (5¾ 5b0 external. in addition to the winding welds (6a, 6b), and the space between the inner casing of said sleeve and the internal duct of the set of ooaxia ducts between the two welds of (6a. 6b) winding be filled with an insulating material, of preferably, a tase changing compound, preferably still, a molten salt contained at least in a second watertight pouch (20) completely surrounding the refined internal conduit, with the longitudinal end of said pouches, of a preferably in longitudinal axial section, a profile (20o) beveled in order to fit as close as possible to said external conduit 15 after the enclosure zone (6a. 6b) between said conduit (5a _it 5b ü external and the said housing (1b) hell of said sleeve. 12. A set of coaxial ducts according to claims 1 to 10, characterized in that each said unitary element of coaxial ducts comprises, at its end, said piece (9a, 9b) of 20 junction, the two said junction pieces being connected by welding (7) between them one of said junction pieces comprising, on its external surface, a protuberance in the form of a stop or collar (30) able to allow the retention, in suspension, of the unit of coaxial duct unit connected to it when it is in a vertical or inclined position 26, from a vessel (21) installed at sea. and said tubular sleeve comprises an end zone with an inner casing with a diameter (35a) greater than that of the opposite end (35b) in the longitudinal direction, said end zone of the larger outer casing (35a) covering the set of conduits coaxials within said sleeve, skin less, from said protuberance or collar (30). 13. Coaxial conduit set according to claim 7 or 11, characterized in that said sleeve involves said 5/5 first and second bags forming two rafts (22a, 22b and 20a, 20b) diametrically opposite semi-cylindrical on one side and the other of the coaxial conduit set. 14. Coaxial conduit set. according to one of the 5 vindications ia 2, characterized in that the length of said sleeve is comprised between 1 to 10 m, preferably from 2 to 6 m, preferably with a thickness of 5 to 25 cm, still more preferably. showing said inner (14) and outer (1a) casings of the tubular wall of the sleeve (1) a thickness of 2 to 10 mm. 10 15, Tubular wall thermal insulation sleeve (1) filled with an incomparable thermal insulation material as defined in one of claims 1 to 14.